1. Field of the Invention
The present invention relates to a method of and apparatus for vertically positioning conditioning devices, e.g., edge roll wheels, heaters, coolers, and/or linear induction motors, in a glass forming chamber.
2. Description of the Technical Problem
In the manufacture of flat glass, molten glass exits a furnace onto a pool of molten metal, where it advances downstream and is controllably cooled to form a glass ribbon. During the process of forming the glass ribbon on the molten metal pool it is often desirable to act on the ribbon and/or the molten metal pool with devices inserted into the forming chamber, e.g., ribbon edge gripping devices, heating devices, cooling devices, and molten metal circulating devices. There is a need when utilizing such devices for a technique which assures their accurate positioning within the bath with respect to the surface of the molten metal pool.
For example, edge roll devices are generally inserted in opposed pairs into the forming chamber to exert longitudinal and outwardly lateral components of force upon the marginal edge portions of the ribbon. The depth of engagement, or bite, of each edge roll wheel with the ribbon determines in part the magnitude of the force exerted thereby. To equalize the force exerted by each one of a pair of opposed edge rolls, the bite must be determinable and controllable. An imbalance in forces may result in ribbon instability or dislocation.
Numerous patents teach methods of and apparatus for detecting the horizontal location of and/or the positioning of devices relative to the marginal edge of a ribbon of glass in a forming chamber, including U.S. Pat. Nos. 3,482,954; 3,500,548; 3,805,072; 3,977,858; 3,998,616; and 4,008,062. None of the referenced patents, however, teach a method of or apparatus for vertically positioning devices relative to the surface of the molten metal pool, e.g., to determine bite depth of an edge roll wheel.
U.S. Pat. No. 2,380,436 to Holdman generally teaches apparatus for indicating the level of molten glass in a melting tank, including a fluid cooled shaft which extends into the melting tank and supports an electrical contact therein. The level of the molten glass is generally detected by rotating the electrical contact into engagement with the electrically conductive molten glass to generate an electrical signal. While useful for the purpose of monitoring electroconductive fluid levels, the subject patent does not address the problem of conveniently vertically positioning conditioning devices in a glass forming chamber.
U.S. Pat. No. 4,078,911 to Green et al. generally teaches a method of determining the relative elevations of components of a float glass facility, in which the surface of the molten metal bath is utilized as a reference plane. Generally, the elevation of an adjustably mounted structural component of the float glass facility is determined relative to the surface of the pool of molten metal through the use of a surveyor's level, a reference scale, and a vertically adjustable gauge device. An arm of the gauge device is inserted into the float chamber and a probe mounted thereto is lowered into point contact with the pool of molten metal. An electrical signal may be generated to indicate the occurrence of such point contact. The surveyor's level is then utilized to observe the relative elevations of a reference mark on the probe and a reference point on the structural component the position of which is to be determined. While the disclosed technique may be useful in accurately determining relative elevations in a float glass facility, it may prove cumbersome and time consuming when utilized to reposition relatively portable conditioning devices within the float chamber. It would be advantageous to have a method of and apparatus for conveniently vertically positioning conditioning devices within a float chamber which avoids the limitations previously noted.